Electrophoresis is a well known technique for the separation of a charged species by utilizing their differences in rate of migration under the influence of an electrical field. The procedure has proved invaluable for the resolution and isolation of complex biological substances such as enzymes, serums, carbohydrates, proteins, DNA and RNA. Most analytical electrophoresis methods are based on zone-electrophoresis in which a thin zone of a sample material is applied to the electrophoretic medium. The electrophoretic migration of the sample components results in the formation of fractional zones. These zones can be examined and studied by applications of standard electrophoretic practice such as fixing, staining and washing to remove buffers. Desirably, the electrophoretic media is a thin gel film coated on a suitable support, commonly glass or plastic. Such an arrangement permits the electrophoretic separation to be achieved in a minimum of time with a maximum degree of resolution.
Various hydrophilic colloids, for example, starch, agarose and cellulose derivatives have been used in forming electrophoretic gel films, but polyacrylamide is preferred. One reason for preferring polyacrylamide is that gels can be prepared from it having a wide range of pore size. This is accomplished primarily by varying the ratio of acrylamide polymer to the N, N', methylenebisacrylamide cross-linking reagent.
The resulting polyacrylamide gels provide high resolution electrophoretic separation of important biopolymers, for example, proteins and nucleic acids. In addition, the absence of ionized groups in polyacrylamide gels render such gels suitable as an anticonvection medium for isoelectric focusing.
Once the electrophoretic techniques have been applied in order to separate the materials in the gel, it is necessary to transfer the separated materials from the gel to a support where they can be tested. A number of procedures are available for transferring the electrophoretically resolved materials from the gel. One such procedure involves electro-blotting. This type of transfer procedure involves transferring the resolved bands within the gel to a support matrix such as a nitrocellulose sheet. The transfer is carried out by the application of an electric field and therefore is distinguishable from a more conventional alternative which involves the capillary transfer of such materials usually used in techniques such as southern and northern blotting.